Engineering, conjugation, and immunogenicity assessment of Escherichia coli O121 O antigen for its potential use as a typhoid vaccine component

Glycoconj J. 2013 Jul;30(5):511-22. doi: 10.1007/s10719-012-9451-9. Epub 2012 Oct 6.

Abstract

State-of-the-art production technologies for conjugate vaccines are complex, multi-step processes. An alternative approach to produce glycoconjugates is based on the bacterial N-linked protein glycosylation system first described in Campylobacter jejuni. The C. jejuni N-glycosylation system has been successfully transferred into Escherichia coli, enabling in vivo production of customized recombinant glycoproteins. However, some antigenic bacterial cell surface polysaccharides, like the Vi antigen of Salmonella enterica serovar Typhi, have not been reported to be accessible to the bacterial oligosaccharyltransferase PglB, hence hamper development of novel conjugate vaccines against typhoid fever. In this report, Vi-like polysaccharide structures that can be transferred by PglB were evaluated as typhoid vaccine components. A polysaccharide fulfilling these requirements was found in Escherichia coli serovar O121. Inactivation of the E. coli O121 O antigen cluster encoded gene wbqG resulted in expression of O polysaccharides reactive with antibodies raised against the Vi antigen. The structure of the recombinantly expressed mutant O polysaccharide was elucidated using a novel HPLC and mass spectrometry based method for purified undecaprenyl pyrophosphate (Und-PP) linked glycans, and the presence of epitopes also found in the Vi antigen was confirmed. The mutant O antigen structure was transferred to acceptor proteins using the bacterial N-glycosylation system, and immunogenicity of the resulting conjugates was evaluated in mice. The conjugate-induced antibodies reacted in an enzyme-linked immunosorbent assay with E. coli O121 LPS. One animal developed a significant rise in serum immunoglobulin anti-Vi titer upon immunization.

MeSH terms

  • Animals
  • Antibodies, Bacterial / biosynthesis
  • Campylobacter jejuni / chemistry
  • Campylobacter jejuni / genetics
  • Campylobacter jejuni / immunology
  • Carbohydrate Sequence
  • Escherichia coli / chemistry
  • Escherichia coli / genetics
  • Escherichia coli / immunology
  • Female
  • Glycoconjugates / chemistry
  • Glycoconjugates / immunology
  • Glycosylation
  • Hexosyltransferases / chemistry
  • Hexosyltransferases / genetics
  • Hexosyltransferases / immunology*
  • Membrane Proteins / chemistry
  • Membrane Proteins / genetics
  • Membrane Proteins / immunology*
  • Mice
  • Molecular Sequence Data
  • O Antigens / chemistry
  • O Antigens / genetics
  • O Antigens / immunology*
  • Polysaccharides, Bacterial / chemistry
  • Polysaccharides, Bacterial / genetics
  • Polysaccharides, Bacterial / immunology*
  • Protein Engineering
  • Salmonella typhi / drug effects*
  • Salmonella typhi / immunology
  • Salmonella typhi / pathogenicity
  • Typhoid Fever / immunology
  • Typhoid Fever / microbiology
  • Typhoid Fever / prevention & control*
  • Typhoid-Paratyphoid Vaccines / administration & dosage
  • Typhoid-Paratyphoid Vaccines / chemistry
  • Typhoid-Paratyphoid Vaccines / genetics
  • Typhoid-Paratyphoid Vaccines / immunology*
  • Vaccines, Conjugate

Substances

  • Antibodies, Bacterial
  • Glycoconjugates
  • Membrane Proteins
  • O Antigens
  • O-antigen, E.coli O121
  • Polysaccharides, Bacterial
  • Typhoid-Paratyphoid Vaccines
  • Vaccines, Conjugate
  • capsular polysaccharide, Salmonella
  • Hexosyltransferases
  • dolichyl-diphosphooligosaccharide - protein glycotransferase